Electron Probe Microanalysis of Nitrogen in Glasses and Glass Ceramics

 A homogeneous (phosphate glass) and a heterogeneous (glass ceramic) material were chosen to develop a method for electron microprobe analysis of nitrogen in glasses and glass ceramics. The metaphosphate (50 mole-% P₂O₅, 25 mole-% BaO, 25 mole-% Rb₂O) base glass and the silicate glass (composition of the base glass: 6.9 mole-% Al₂O₃, 21.3 mole-% MgO, 47.3 mole-% SiO₂, 5.1 mole-% CaO, 19.4 mole-% AlN) were melted and cooled down to room temperature. In a second step, the two materials were nitrided by applying dry NH₃ in a special tube furnace. Up to 5 wt.-% of nitrogen could be introduced. The ability of energy dispersive (EDX) as well as wavelength dispersive (WDX) electron probe microanalysis to analyze low contents of light elements in combination with highly concentrated heavy elements was tested both for glasses and for glass ceramics. Measuring conditions had to be optimized to get reliable analytical results as well as to avoid radiation damage of the glasses which may occur especially in the case of wavelength dispersive X-ray analysis. The results were compared with two different analytical methods: inductive coupled plasma analysis and a commercial nitrogen-oxygen-analyzer (the specimen is decomposed by heating and the released gases are analyzed spectroscopically (O) and electrically (N)).